1. Field of the invention
The present invention relates to audio communication systems, and, more specifically, to underwater audio communication systems.
2. Description of the related art
Most modern personal audio communication systems do not use bone conduction for sound transmission to the ear. Instead, sound is transmitted by air conduction to the ear canal where it is subsequently conducted through the middle ear to the cochlea where these vibrations are interpreted in the brain as sound. Examples of these systems are many from hand held 2 way radios, to FM and AM radios, to short and long wave radio communication systems. All of these rely on air conducted sound for the listener and speaker.
Several disadvantages of this type of system are found for underwater swimming. First, in order to facilitate an air gap between the ear and the sound source, it is necessary to provide a mask with an apparatus over the ears or a helmet covering the entire head. Some systems provide sound directly to the ear by placing a sound source against the outside of the outer ear. This has been the conventional approach for several years. While this approach is effective and provides for communication, this system is very expensive, cumbersome to use, is uncomfortable, requires special training for use, and provides poor sound quality. Further, such a system introduces a process and equipment which is very different from conventional scuba diving equipment, whereby in the case of an underwater loss of air, a buddy assistance measure requiring sharing of air is ineffective.
The helmet or full face hood currently used for communication is also more dangerous to the user in the event that water enters the air gap space in the hood because it is more difficult to clear the water from the intended air space due to the increased air volume and sealing surface than a normal mask which only covers the eyes and nose. A user's ability to obtain air for breathing also is impaired if problems occur with the full face hood, making it more dangerous than normal scuba diving gear.
Commercial units which rely on air conduction or direct ear contact sound transmission are currently available. Brand names and constructions are differentiated primarily on the type of sonar carrier, frequency of transmission, power, type of transmission send switch, transducer types and headgear configurations. This type of diving apparatus is shown in U.S. Pat. No. 3,789,353 to Hunter.
Examples of conventional audio listening systems without headphones are shown in U.S. Pat. No. 4,589,134 to Waldron for a sound system enclosed in a vest meant to be worn by the listener; U.S. Pat. No. 4,070,553 to Hass, for a scarf-tube enclosing a sound source meant to be worn around the listener's neck; U.S. Pat. No. 3,869,584 to Wilde, covering a device enclosing the ears of the individual listener; and U.S. Pat. No. 3,868,572 to Kaufman, representative of personal audio devices worn inside the ear of the individual listener.
Conventional bone conduction audio devices are typically hearing aids for the hearing impaired. Examples of such bone conduction hearing aids are disclosed in U.S. Pat. No. 2,230,500 to Lybarger; U.S. Pat. No. 2,258,638 to Zarth; and West German Patent No. 2451977 to Breckwoldt. Most modern bone conduction hearing aids include the ability to implant the bone conduction oscillator beneath the listener's skin in direct contact with the mastoid bone.
Particular to tooth oscillated bone conduction is U.S. Pat. No. 5,033,999 to Mersky, which is representative of a method and apparatus for endodontically augmenting hearing by the direct encapsulation of an audio transducer inside a tooth.
What is needed in the art is an underwater communication system which provides effective one-way or two-way communication with a diver, and which does not include the inherent problems associated with conventional systems using air conduction to transmit the sound waves through the ear canal.